Methods and Apparatus for Manufacture of a Reclosable Plastic Carton

ABSTRACT

A carton formed from a unitary blank for storing food within and methods of manufacture of the carton therefrom, are disclosed herein. The carton comprises a generally rectangular bottom having a pair of major bottom flaps and a pair of minor bottom flaps that are folded to form a substantially closed bottom, and a pair of major side panels, a pair of minor side panels, and a secondary side panel that are folded perpendicular to the bottom. An opening is defined by the upper ends of the major side panels and the minor side panels opposite the bottom and is generally non-rectangular.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.11/268,251, filed on Nov. 7, 2005, which is hereby incorporated byreference in its entirety.

FIELD

This disclosure relates generally to a reclosable plastic carton forfood products, such as cereals, snack crackers and other such foods, andmethods of manufacture, and more specifically to a reclosable plasticcarton that is assembled from a single carton blank.

BACKGROUND

Cereals, snack crackers, and other similar foods are typically packagedin paperboard cartons. Typical paperboard cartons do not alone protectproducts. As a result, the food product is commonly packaged within aninner sealed bag or liner that is placed inside the paperboard carton.To open the inner bag, the consumer must first open the box top flaps,then open the inner bag. Once this inner bag is opened, the integrity ofthe seal of the inner bag is lost. To reclose the bag, consumers resortto rolling the top of the bag or placing a clip or tape on the top ofthe bag. Carton flaps can be brought together to close the carton top,and secured using a tongue and slot connection. These options do notrestore the integrity of the seal.

The typical carton and bag combination adds to the complexity inmanufacturing and can increase the number of materials and steps neededto create the bag and carton combination. Furthermore, the bag formingand filling speed is often much slower than the carton forming speed,and thus may limit the speed of the total process. For example, thecartons may be formed at 250 cartons per minute, while the bags are onlyformed and filled at 50 bags per minute.

A plastic carton, manufactured by Paper Machinery Corporation, consistsof a carton having a reclosable lid. The food product is packageddirectly in the carton, without first being placed in a bag or liner.The carton is made up of two carton blanks, one blank for assembly ofthe carton sides and another blank for assembly of the carton bottom.However, the assembly of the bottom of the carton to the rest of thecarton during manufacturing can add to the cost and complexity ofmanufacturing.

SUMMARY

A plastic carton formed from a unitary blank for storing food products,and methods of manufacture of the carton, are disclosed herein. Thecarton comprises a pair of major bottom flaps and a pair of minor bottomflaps that are folded to form a substantially closed bottom, generallyrectangular, and a pair of major side panels, a pair of minor sidepanels, and a secondary side panel that are each perpendicular to thebottom. An opening is defined by upper ends of the major side panels andthe minor side panels opposite the bottom, and is generallynon-rectangular. The opening has a rim around its peripheral edges witha width greater than the thickness of the side panels. The bottom flapsare sealed to adjacent bottom flaps, and the secondary side panel issealed to one of the other side panels to form an enclosed interiorsuitable for containing a food product. When used in conjunction with alid, the carton can conveniently store food directly in its interiorwhile eliminating the need for an additional bag liner or the like. Inaddition, such cartons provide for simplified reclosability to improvefreshness while reducing the manufacturing time as compared to typicalcarton and bag combinations.

Methods of forming the carton from a unitary blank, and from a unitaryblank in a collapsed configuration, are disclosed. The blank has a pairof major side panels and a pair of minor side panels. A pair of majorbottom flaps and a pair of minor bottom flaps are attached to the sidepanels at lower ends thereof. In a collapsed configuration, a first setof the major and minor side panels are generally coplanar, and a secondset of the major and minor side panels are also coplanar, with the firstand second sets partially overlying or being adjacent to one another. Asecondary side panel is attached lengthwise to an interior edge of oneof the major and minor side panels. The collapsed blank is assembledinto a carton by folding the major and the minor side panels normal toadjacent side panels and by folding the bottom flaps into configurationsnormal to the side panels. A heat source is applied to the bottom flapsto form seals therebetween. A heat source is also applied to the openingdefined by the upper edges of the major and minor side panels to shapethe upper edges into a non-rectangular periphery having a rim.

In a further aspect of the carton, the carton comprises a reclosable lidthat has a channel about its periphery and on its underside forreceiving the rim. A removable film may be attached to the rim andextend over the opening to provide a seal.

In a further aspect of the method, the bottom flaps may be sealed byapplying a heat source from the exterior side of the carton and pressinga bottom anvil of a forming tool against the bottom flaps from theinterior of the carton. The non-rectangular opening and the rim aboutthe opening may be formed by a top mandrel of the forming tool.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a perspective view of an assembled reclosable plastic carton;

FIG. 1B is a sectional view of the rim of the carton and the lid takenalong line 1B-1B of FIG. 1A;

FIG. 2 is a plan view of a plastic carton blank prior to assembly;

FIG. 3A is a perspective view of the plastic carton blank of FIG. 2 withmajor side panels folded into perpendicular orientations relative tominor side panels and a secondary side panel sealed to one of the majorside panels;

FIG. 3B is a perspective view of the plastic carton of FIG. 3A with theminor bottom flaps folded into perpendicular orientations relative tothe side panels;

FIG. 3C is a perspective view of the plastic carton of FIG. 3B with themajor bottom flaps folded into perpendicular orientations relative tothe side panels;

FIG. 3D is a perspective view of the plastic carton of FIG. 3C prior tosealing the bottom flaps, and showing a heated sealing bar, anvil and amandrel;

FIG. 3E is a perspective view of the plastic carton of FIG. 3D, with theheated sealing bar applied against the exterior of the bottom flaps andthe anvil applied against the bottom interior;

FIG. 3F is a perspective view of the plastic carton of FIG. 3E, with themandrel shaping the opening and forming the rim; and

FIG. 4 is a perspective view of a flow diagram of a filling and sealingprocess of the formed plastic carton of FIG. 1.

DETAILED DESCRIPTION OF THE DRAWINGS

A reclosable plastic folded carton, and in particular a reclosableplastic carton used for packaging cereals, snack crackers and othersimilar foods, and methods of manufacture, are disclosed herein andillustrated in FIGS. 1-4. The reclosable plastic carton is substantiallysealed, and may be hermetically sealed, such as by using heat welding,thus avoiding the need to glue the carton together, and is made of aplastic material that is compatible with use in food contact. Theplastic carton eliminates the need for addition of an inner liner bagbecause the plastic carton provides the barrier properties of the liner,and thus can reduce cost and manufacturing effort. The cartons areassembled from a one-piece blank. The top opening may initially besealed with a tamper-evident barrier film, and a reclosable lid can beprovided to permit reclosing of the carton to help maintain thefreshness of the food after the carton is initially opened.

The reclosable plastic carton 10, as illustrated in FIG. 1A, is made ofa plastic sheet blank 20 that is folded and assembled into a carton 10.The carton 10 has an interior and an exterior area; the interior area isused for containing food and the exterior area is suitable forapplication of printing, such as prior to or after formation of thecarton, and labels that convey what type of product is packaged inside.

The carton is generally sized about the same as typical cereal cartons,although other sizes of the carton can be made. The carton has a frontpanel 18 a and a back panel 18 b, and two side panels 18 c and 18 dconnecting the front panel 18 a to the back panel 18 b. The bottom 14 ofthe assembled carton 10 is generally rectangular. The top of the carton10 has a non-rectangular shape; in particular it may be an oval shape.The top edge of the carton 10 has a rolled lip or rim 58 about theperiphery of the top opening 44 (see FIG. 1B). The rolled rim 58 isdesigned to receive a lid 12, which may be a reclosable lid or a hingedlid that is configured to mate with the rim 58. A film can be placedacross the top opening before the lid 12 is placed thereover to providean initial seal.

The carton 10 preferably provides similar barrier properties as that ofa liner bag and eliminates the need of an additional bag inside of thecarton 10. The plastic carton 10 may be made from materials such aspolypropylene, high density polyethylene, and polyethyleneterephthalate, as well as possibly including multiple layers thereof andstill further a barrier layer, such as ethylene vinyl alcohol. Thecarton may also be made from a material having a plastic coating. Thecarton 10 is generally used to package cereals, snack crackers, cookies,rice, stuffing, cake mixes, dry desserts, and other similar dried foods,but may also be used for various other foods such as coffee and instantbeverage powders.

In its unfolded configuration, the plastic carton blank 20, as shown inFIG. 2, is a unitary sheet of plastic with an inner side 22 and an outerside 24. The material of construction used for the carton blank 20 ispreferably polypropylene, but alternatively other types of plasticcarton material may be used that can be folded into a carton and sealed,as discussed herein. The outer side 24 of the blank 20 may bepre-printed with indicia and the inner side 22 may be marked with scoredlines 26 a and 26 b to aid in folding of the blank 20. In addition, oneor more scored lines may be made in the corners to help create asmoother radius when folded. The inner side 22 of the blank 20 definesthe interior area of the assembled carton 10, and the outer side 24 ofthe blank 20 becomes the exterior area of the carton 10.

The scored lines 26 a and 26 b divide the unitary carton blank 20 intovarious segments or panels such that there are at least four bottomflaps 33 and at least four side panels 31 in a coplanar arrangement. Thetwo larger width panels represent the major side panels 28 and the twosmaller width panels represent the minor side panels 30. The major sidepanels 28 comprise one front panel and one back panel and the minor sidepanels 30 are disposed therebetween when the carton blank 20 is erectedinto the carton 10. Preferably the carton blank 20 has a secondary sidepanel 32 that is of a narrower width than the major and minor sidepanels 28 and 30, but is about the same length as the major and minorside panels 28 and 30. Alternatively, the score lines 26 a may be splitinto two lines between adjacent side panels, instead of one, with thescore line starting out as a single line from the bottom flaps andsplitting into two lines about one-third of the way from the bottomflaps. This split score line may further aid in facilitating theformation of the round carton edges, which are discussed below.

Adjacent the set of side panels 31, including the major side panels 28,the minor side panels 30, and the secondary side panel 32 is a set offlaps 33 for forming the bottom of the carton 10 when assembled. Theflaps 33 include a pair of major bottom flaps 36 and a pair of minorbottom flaps 34. The major bottom flaps 36 are approximately the samewidth as the major side panels 28 and are attached via a fold or scoreline 26 b thereto; the bottom minor flaps 34 are approximately the samewidth as the minor side panels 30 and are likewise attached to thebottom fold or score line 26 b of the minor side panels 30. The width ofeach flap 33, parallel to the fold line 26 b, decreases between the foldline 26 b and the opposite end of each flap 33. The decreasing widths ofthe flaps 33 result in tapered side edges which provide a clearancespacing between edges of adjacent flaps 33 when folded perpendicular tothe side panels 31. The angle of taper of each side may be between about1 and 5 degrees, and is preferably about 3 degrees. If the angle oftaper is about 3 degrees then the total tapered angle between twoadjacent flaps would be about 6 degrees.

In one particular example, the unfolded carton blank 20 may generallyconsist of a sheet from about 14 inches to about 18 inches in width andfrom about 7.3 inches to about 11.3 inches in length, more preferablythe dimensions are about 16 inches by 9.30 inches; the width of theblank 20 also includes the width of the secondary side panel 32. Thevertical length of the individual major side panels 28 and the minorside panels 30 as well as the secondary side panel 32 may be from about5.7 inches to about 9.7 inches, more preferably about 7.7 inches. Themajor side panels 28 may have a width of about 3.3 inches to about 7.3inches, more preferably about 5.3 inches. The minor side panels 30 mayhave a width of about 0.5 inches to about 4.5 inches, more preferablyabout 2.5 inches. Each individual side panel forms a substantiallystraight-edged rectangle. The secondary side panel 32 has the samelength as the side panels, but a width much smaller; from about 0.25inches to about 1 inch, more preferably about 0.50 inches. The majorbottom flaps 36 and the minor bottom flaps 34 each have a verticallength of from about 0.50 inches to about 3.5 inches, more preferably atabout 1.5 inches. The width of the major bottom flaps 36 and the minorbottom flaps 34 is similar to the widths of the major 28 and minor 30side panels, respectively. Although these dimensions are described forone particular example, these dimensions may be varied to obtain othercarton sizes.

Turning now to the assembly of the carton blank 20, each of the sidepanels 31 are folded along the score lines 26 a into a generallyperpendicular arrangement with the adjacent side panels 31. A heatsource, such as an ultrasonic or standard conduction heat source, isapplied to the outer exterior side 24 of the blank 20 where thesecondary side panel 32 and the major side panel 28 overlap. Theapplication of a heat source, preferably a heat bar, to the outerexterior side 24 heat seals the secondary side panel 32 to the interiorof the major side panel 28. The seal is formed by heating thepolypropylene carton material to form a bond between the secondary sidepanel 32 and the interior of the major side panel 28. The temperature ofthe heat source depends upon the melting point of the type of cartonmaterial and may be the same as or slightly higher than the meltingpoint temperatures of the carton material, with melting points varyingfrom about 230° F. to about 485° F., and preferably from about 250° F.to about 350° F. The temperature of the heat source used to form therolled rim of the carton needs only to reach a deflection temperature orVicat softening point, which for example, may be about 100° F. to about200° F. for polypropylene. Alternatively, a separate heat-activatedcoating or sealant layer may be applied to the blank 20 to aid informing the seals.

After folding the side panels 31 and sealing the secondary side panel 32to the major side panel 28, the carton blank 20 has been converted tothe partially assembled, erect configuration having open ends, such asillustrated in FIG. 3A. Prior to being erected, but after the sealing ofthe secondary side panel 32 to the interior of the major side panel 28,the collapsed carton may have a first set of the major and minor sidepanels generally coplanar and a second set of the major and minor sidepanels generally coplanar, with the first set partially overlying thesecond set. From this collapsed configuration, the carton can be shiftedto the erect configuration illustrated in FIG. 3A.

From the erect configuration, the major bottom flaps 36 and minor bottomflaps 34 are folded such that they are substantially normal to therespective side panels 31. A guide or folding arm may be used to foldthe two minor bottom flaps 34 (see FIG. 3B) as the carton 100 isdirected along a conveyor. Another guide or folding arm may be used tofold the two major bottom flaps 36 against the minor bottom flaps 34, asthe carton is continued to be directed along the conveyor to result in afolded carton 100 that is generally rectangular, as shown in FIG. 3C.

A forming tool 40 is used to shape the opening 44 of the carton 100 andassist in the sealing of the bottom flaps 33 to each other. Morespecifically, a bottom anvil 48 is used to assist in the sealing of thebottom flaps 33 to each other. The bottom anvil 48 is attached to oneend of a reciprocating rod 50 and can be inserted and removed from theinterior of the carton 100, as designated by the direction of arrows Aand B. When inserted, the bottom anvil 48 is pressed against theinterior side of the bottom flaps 33 to provide a backing surfaceagainst which a heated sealing bar 42 can press the flaps 33 to seal thebottom 60, as described in greater detail below. The top mandrel 46 isindependently slidable along the reciprocating rod 50, also designatedby the direction of arrows A and B, and can be selectively applied tothe opening 44 of the carton 10 to both reshape the rectangular opening44 into a rounded opening and to form a rim or lip at the edge of thecarton opening 44. The top mandrel 46 may be heated to assist in formingthe rim and shaping the carton opening.

Turning now to the use of the forming tool 40, the bottom anvil 48 ofthe forming tool 40, as shown in FIG. 3D, is inserted through the topopening 44 into the interior of the carton 100, and pressed against thefolded bottom flaps 33 from the inside of the carton 100. The bottomanvil 48 of the forming tool 40 is substantially rectangular and sizedto generally match the shape of the bottom 60 of the carton 100.

Once the bottom anvil 48 of the forming tool 40 is placed against theflaps of the bottom interior of the carton 100, the heated sealing bar42 is pressed against the bottom 60 from the exterior area of the carton100, as shown in FIG. 3E. The heated sealing bar 42 presses the flapsagainst the bottom anvil 48 in the direction of arrow C and heats thebottom flaps 60 to create a substantially sealed carton bottom 60.

Subsequent to sealing the bottom flaps or simultaneously therewith, arounded portion of the top mandrel 46 of the forming tool 40 is insertedinto the carton interior through the carton opening 44, as shown in FIG.3F. The rounded portion of the top mandrel 46 of the forming tool 40 hasan oval shape. In addition, the mandrel 46 has a rim forming portion forshaping the edges of the carton opening 44 into the rim 58. The rimforming portion of the mandrel 46 includes surfaces, such as a flatsurface or a channel, for rolling the edges of the carton opening 44into a curved shape, which becomes the rim 58, such as illustrated inFIG. 1B. The rim 58 has a width that preferably will be greater than thethickness of the side panels 31.

The top mandrel 46 is orientated such that its lower section protrudesinto the interior of the carton 100 causing the side panels 31 near theopening 44 to become slightly curved and to bulge out in order toaccommodate a round opening. The curve of the side panels near theopening 44 may further be aided in its formation by the addition ofsplit score lines between adjacent side panels, as previously discussed.Once all the seals have been formed and the rim 58 has been made, theforming tool 40 and heat sources are removed from the interior of thecarton 10.

Subsequent to the carton 10 formation, the carton 10 is filled with afood product 54, as shown in FIG. 4. Any known filling means may beutilized to add the food product 54 to the interior of the carton 10,such as, for example, a funnel 52. After the carton 10 has been filled,a seal or barrier film 56 may be placed over the opening 44 of thecarton 10 and attached to the rim to seal the opening 44, and maintainproduct freshness prior to opening of the carton 10. In addition, thepresence of the barrier film 56 can provide evidence that the carton 10has not previously been opened. Once the barrier film 56 is in place alid 12 may be placed over it. The lid 12 may be either hinged or snappedon and may have a recessed channel about the periphery of an undersideof the lid 12 designed to receive the rim 58. To open the package, thereclosable lid is removed and then the barrier film, and to close thecarton the reclosable lid is snapped back down over the opening tosubstantially reseal the carton 10.

From the foregoing, it will be appreciated a reclosable plastic cartonis provided that allows for storing food directly in the carton withoutalso requiring a bag liner to maintain freshness or to separate it fromthe carton, and for permitting removal of a quantity of food andallowing continued storage of the remaining food while maintaining itsfreshness. However, the disclosure is not limited to the aspects andembodiments described hereinabove, or to any particular embodiments.Various modifications to the carton, the blank, and methods ofassembling can result in substantially the same carton.

1. A carton formed from a unitary blank, the carton comprising: agenerally rectangular bottom with a pair of major bottom flaps and apair of minor bottom flaps where the bottom flaps are folded to form asubstantially closed bottom; a plurality of upstanding side panels,including a pair of major side panels, a pair of minor side panels, anda secondary side panel, where the side panels are each folded generallyperpendicular to the bottom, the major and minor side panels areattached to the bottom at a lower end thereof and the secondary sidepanel is attached to one of the major side panels or one of the minorside panels; and an opening defined by upper ends of the major sidepanels and the minor side panels opposite the bottom that is generallynon-rectangular and having a rim around a peripheral edge thereof, therim having a width greater than the thickness of the side panels.
 2. Thecarton formed from a unitary blank in accordance with claim 1, whereinthe carton further comprises a reclosable lid, the lid having a channelabout a periphery of an underside thereof for receiving the rim of theopening.
 3. The carton formed from a unitary blank in accordance withclaim 1, wherein the carton further comprises a film attached to the rimof the carton to seal the opening.
 4. The carton formed from a unitaryblank in accordance with claim 1, wherein the secondary side panel issealed to one of the other side panels.
 5. The carton formed from aunitary blank in accordance with claim 4, wherein the bottom flaps aresealed to adjacent bottom flaps to form an enclosed interior forcontaining a food product.
 6. The carton formed from a unitary blank inaccordance with claim 1, wherein the rim has a rolled lip about theperipheral edge.
 7. The carton formed from a unitary blank in accordancewith claim 1, wherein the carton is made of one or more materialsselected from the group consisting of polypropylene, high densitypolyethylene, and polyethylene terephthalate.
 8. The carton formed froma unitary blank in accordance with claim 7, wherein the carton furtherhas a barrier layer.
 9. The carton formed from a unitary blank inaccordance with claim 8, wherein the barrier layer comprises ethylenevinyl alcohol.
 10. The carton formed from a unitary blank in accordancewith claim 1, wherein an outer surface of the carton is suitable forprinting indicia or other markings.
 11. The carton formed from a unitaryblank in accordance with claim 1, wherein the carton is used for storingfood products selected from the group consisting of rice, stuffing,cereal, cookies, crackers, cake mixes, dry desserts, coffee and instantbeverages.
 12. A carton formed from a unitary blank in accordance withclaim 1, wherein the opening is oval and the side panels aresubstantially rectangular in shape.
 13. A carton formed from a unitaryblank in accordance with claim 1, wherein the secondary side panel has awidth that is less than a width of either the major and minor panels.14. A carton formed from a unitary blank in accordance with claim 13,wherein the secondary side panel has a length that is equal to a lengthof the major and minor panels.
 15. A reclosable food carton comprising:a generally rectangular bottom with a pair of major bottom flaps and apair of minor bottom flaps where the bottom flaps are folded and sealedto adjacent bottom flaps to form a substantially closed bottom; aplurality of upstanding side panels, including a pair of major sidepanels, a pair of minor side panels, and a secondary side panel, wherethe side panels are each folded generally perpendicular to the bottom,the major and minor side panels are attached to the bottom at a lowerend thereof and the secondary side panel is attached to one of the majorside panels or one of the minor side panels and is sealed to the otherof the major side panels or the minor side panels forming an enclosedinterior having side panels generally rectangular in shape; a generallyoval opening defined by upper ends of the major side panels and theminor side panels opposite the bottom and having a rim around aperipheral edge thereof; and a reclosable lid having a channel about aperiphery of an underside thereof for receiving the rim of the opening.16. The reclosable food carton in accordance with claim 15, wherein therim has a width greater than the thickness of the side panels.
 17. Thereclosable food carton in accordance with claim 15, wherein the cartonis made of a material having barrier properties.
 18. The reclosable foodcarton in accordance with claim 17, wherein the material having barrierproperties is one or more materials selected from the group consistingof polypropylene, high density polyethylene, and polyethyleneterephthalate.
 19. The reclosable food carton in accordance with claim15, wherein the secondary side panel is attached to one of the minorside panels and is sealed to an interior of one of the major sidepanels.